A pair of T-Minus Engineering DART missions that were slated to be launched from Esrange in Sweden last week faced -35°C temperatures, causing one of the flights to malfunction and the other to be called off.

The first of the two missions was launched on 7 February from the brand-new Launch Complex 3 at the Esrange Space Center. Following a five-second burn, the separation of the 2.3-metre booster was completed successfully. While this initially appeared to be a textbook launch, an anomaly occurred 12 seconds into the flight, resulting in the early deployment of the mission’s payload. The rocket carried a wave propagation experiment and a Langmuir probe for Sweden’s KTH Royal Institute of Technology.

In response to questions from European Spaceflight, T-Minus explained that the payload was likely ejected passively instead of being actively triggered by the rocket’s onboard computer. The company is currently attributing the anomaly to the cold conditions.

Prior to the launch, T-Minus had told European Spaceflight that it had made a number of modifications to its DART rocket to deal with the cold temperatures, including the installation of heaters. The measures did, however, not go far enough.

“In the future, we’ll likely heat both the booster and dart with warm air until the moment of launch to keep the temperature above freezing,” explained T-Minus CEO Hein Olthof. “However, we’re happy that we could prove that the booster performs well in the lowest temperature region of its usage envelope.”